Integrated chip with inter-wire cavities

ABSTRACT

The present disclosure relates to an integrated chip comprising a substrate. A first conductive wire is over the substrate. A second conductive wire is over the substrate and is adjacent to the first conductive wire. A first dielectric cap is laterally between the first conductive wire and the second conductive wire. The first dielectric cap laterally separates the first conductive wire from the second conductive wire. The first dielectric cap includes a first dielectric material. A first cavity is directly below the first dielectric cap and is laterally between the first conductive wire and the second conductive wire. The first cavity is defined by one or more surfaces of the first dielectric cap.

REFERENCE TO RELATED APPLICATION

This Application is a Divisional of U.S. application Ser. No. 17/355,613, filed on Jun. 23, 2021, the contents of which are hereby incorporated by reference in their entirety.

BACKGROUND

Modern day integrated chips contain millions of semiconductor devices. The semiconductor devices are electrically interconnected by way of back-end-of-the-line (BEOL) metal interconnect layers that are formed above the devices. A typical integrated chip comprises a plurality of BEOL metal interconnect layers including different sized metal wires vertically coupled together with metal vias.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

FIG. 1A illustrates a cross-sectional view of some embodiments of an integrated chip comprising a first metal wire and a second metal wire that are laterally separated by a first cavity.

FIG. 1B illustrates a top view of some embodiments of the integrated chip of FIG. 1A.

FIG. 2 illustrates a cross-sectional view of some alternative embodiments of the integrated chip of FIG. 1A in which a first dielectric cap over the first cavity has a curved lower surface.

FIG. 3 illustrates a cross-sectional view of some alternative embodiments of the integrated chip of FIG. 1A in which the first cavity is defined by one or more surfaces of a first residual sacrificial structure.

FIG. 4 illustrates a cross-sectional view of some alternative embodiments of the integrated chip of FIG. 1A in which the first cavity is defined by a first dielectric cap and a residual dielectric structure.

FIG. 5 illustrates a cross-sectional view of some alternative embodiments of the integrated chip of FIG. 1A in which a first residual capping structure is over the first metal wire and a second residual capping structure is over the second metal wire.

FIG. 6A illustrates a cross-sectional view of some alternative embodiments of the integrated chip of FIG. 1A in which a first dielectric cap surrounds the first cavity.

FIG. 6B illustrates a cross-sectional view of some alternative embodiments of the integrated chip of FIG. 6A in which the first cavity has a different size and/or shape than a second cavity.

FIG. 6C illustrates a cross-sectional view of some alternative embodiments of the integrated chip of FIG. 6A in which a first residual capping structure is over the first metal wire and a second residual capping structure is over the second metal wire.

FIGS. 7-22 illustrate cross-sectional views of some embodiments of a method for forming an integrated chip comprising a first metal wire and a second metal wire that are laterally separated by a first cavity.

FIG. 23 illustrates a flow diagram of some embodiments of a method for forming an integrated chip comprising a first metal wire and a second metal wire that are laterally separated by a first cavity.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

Some integrated chips include one or more semiconductor devices along a substrate and a plurality of metal wires over the substrate that may be electrically connected to the one or more semiconductor devices. The plurality of metal wires are laterally separated from one another by a dielectric layer. The dielectric layer may, for example, comprise silicon oxide, silicon nitride, or some other suitable dielectric.

A challenge with these integrated chips is that a capacitance that exists between the plurality of metal wires contributes to a resistive-capacitive (RC) delay in the integrated chip. The capacitance is proportional to a dielectric constant of the dielectric layer that separates the metal wires. Thus, metal wires that are separated by a material having a high dielectric constant (e.g., about 3.9 for silicon oxide) may exhibit a high capacitance and hence a high RC delay. As a result, a performance of the integrated chip may be low.

Various embodiments of the present disclosure are related to an integrated chip comprising one or more cavities for improving a performance of the integrate chip, and a method of forming the integrated chip for improving a reliability of the integrated chip. For example, an integrated chip comprises an etch-stop layer over a substrate. A first metal wire and a second metal wire are over the etch-stop layer and the second metal wire is laterally adjacent to the first metal wire. The etch-stop layer laterally separates the first metal wire from the second metal wire. A first dielectric cap is directly over the etch-stop layer and laterally between the first metal wire and the second metal wire. A first cavity is directly below the first dielectric cap and directly over the etch-stop layer. The first cavity laterally separates the first metal wire from the second metal wire. Further, the first cavity comprises a first gas and the first cavity is defined by one or more surfaces of the first dielectric cap.

The first gas may, for example, comprise air or some other suitable gas(es) and hence may have a low dielectric constant (e.g., about 1 for air). Thus, by including the first cavity in the integrated chip between the first and second metal wires, a dielectric constant between the first and second metal wires may be low. As a result, a capacitance between the first and second metal wires may also be low and hence an RC delay of the integrated chip may be reduced. Thus, a performance of the integrated chip may be improved.

Further, a method for forming the first cavity may prevent causing damage to the first metal wire and the second metal wire throughout the method. In various embodiments, the method comprises forming a first capping structure over the first metal wire and a second capping structure over the second metal wire before removing a first dielectric structure from between the first and second metal wires with an etch. The first and second capping structures may protect the underlying first and second metal wires from being damaged by the etch. Thus, the first and second metal wires may be undamaged after forming the first cavity. For example, sidewalls and top surfaces of the first and second metal wire may be substantially planar and/or devoid of nanoscopic voids after the first cavity is formed. As a result, a structural integrity of the first and second metal wires may be maintained and hence a reliability of the first and second metal wires may be high.

Referring to FIGS. 1A and 1B simultaneously, FIG. 1A illustrates a cross-sectional view 100 of some embodiments of an integrated chip comprising a first metal wire 110 a and a second metal wire 110 b that are laterally separated by a first cavity 114 a, while FIG. 1B illustrates a top view 150 of some embodiments of the integrated chip of FIG. 1A. The cross-sectional view 100 of FIG. 1A may, for example, be taken across line A-A′ of FIG. 1B.

In such embodiments, the integrated chip comprises a plurality of semiconductor devices 104 along a substrate 102. A first interconnect structure 106 is over the substrate 102. Further, a first etch-stop layer 108 extends over the first interconnect structure 106. Furthermore, a plurality of metal wires 110, a plurality of dielectric caps 112, and a plurality of cavities 114 extend over the first interconnect structure 106.

For example, the first metal wire 110 a and the second metal wire 110 b of the plurality of metal wires 110 extend over the first interconnect structure 106. The first metal wire 110 a is laterally adjacent to the second metal wire 110 b. A first dielectric cap 112 a of the plurality of dielectric caps 112 is directly over the first etch-stop layer 108 and is laterally between the first metal wire 110 a and the second metal wire 110 b. The first dielectric cap 112 a laterally separates the first metal wire 110 a from the second metal wire 110 b along tops of the first and second metal wires 110 a, 110 b. In addition, the first etch-stop layer 108 laterally separates the first metal wire 110 a from the second metal wire 110 b along bottoms of the first and second metal wires 110 a, 110 b.

In some embodiments, top surfaces of the plurality of metal wires 110 are substantially planar (e.g., the first and second top surfaces may not deviate from their respective planes by more than about 1 nanometer, more than about 5 nanometers, more than about 10 nanometers, or some other suitable value). For example, in some embodiments, a first top surface of the first metal wire 110 a and a second top surface of the second metal wire 110 b are substantially planar. Further, in some embodiments, sidewalls of the plurality of metal wires 110 are also substantially planar. For example, in some embodiments, a first sidewall of the first metal wire 110 a and a second sidewall of the second metal wire 110 b that faces the first sidewall are substantially planar.

In some embodiments, sidewalls and top surfaces of the first metal wire 110 a and the second metal wire 110 b are devoid of nanoscopic voids (e.g., nanoscopic defects). For example, in such embodiments, the sidewalls and the top surfaces of the first metal wire 110 a and the second metal wire 110 b are devoid of voids and/or defects that are greater than about 5 angstroms in width, greater than about 1 nanometer in width, greater than about 5 nanometers in width, or some other suitable value.

In some embodiments, the first and second metal wires 110 a, 110 b have first and second theoretical sheet resistances, respectively, and have first and second measured sheet resistances, respectively. In such embodiments, the first measured sheet resistance may differ from the first theoretical sheet resistance by less than 1 percent, less than 5 percent, less than 10 percent, less than 20 percent, less than 30 percent, or some other suitable value. Likewise, the second measured sheet resistance may differ from the second theoretical sheet resistance by less than 1 percent, less than 5 percent, less than 10 percent, less than 20 percent, less than 30 percent, or some other suitable value.

In some embodiments, the first and second metal wires 110 a, 110 b may have any of the aforementioned characteristics (e.g., planar surfaces, surfaces devoid of nanoscopic voids, and/or small differences in measured and theoretical sheet resistances, etc.) because a method for forming the integrated chip may prevent causing damage to the first metal wire 110 a and the second metal wire 110 b throughout the method.

Further, the first cavity 114 a of the plurality of cavities 114 is directly below the first dielectric cap 112 a and is directly over the first etch-stop layer 108. The first cavity 114 a laterally separates the first metal wire 110 a from the second metal wire 110 b. The first cavity 114 a is defined by one or more surfaces of the first dielectric cap 112 a and the first cavity 114 a comprises a first gas. In some embodiments, the first gas may, for example, be or comprise air, some other suitable gas having a low dielectric constant, or the like.

In some embodiments, the first cavity 114 a is defined by an upper surface of the first etch-stop layer 108, a sidewall of the first metal wire 110 a, a sidewall of the second metal wire 110 b, and a lower surface of the first dielectric cap 112 a. In some embodiments, the lower surface of the first dielectric cap 112 a defines a top of the first cavity 114 a. Further, the lower surface of the first dielectric cap 112 a is below a top surface of the first metal wire 110 a and below a top surface of the second metal wire 110 b. In some embodiments, a width of the first cavity 114 a is approximately equal to a distance between the first metal wire 110 a and the second metal wire 110 b.

By including the first cavity 114 a in the integrated chip between the first metal wire 110 a and the second metal wire 110 b, a dielectric constant between the first and second metal wires 110 a, 110 b may be low. As a result, a capacitance between the first and second metal wires 110 a, 110 b may also be low and hence an RC delay of the integrated chip may be reduced. Thus, a performance of the integrated chip may be improved.

In some embodiments, the integrated chip further comprises a second interconnect structure 116 over the plurality of metal wires 110.

Although the first interconnect structure 106 and the second interconnect structure 116 are illustrated generically in FIG. 1 , it will be appreciated that the first interconnect structure 106 and the second interconnect structure 116 may each comprise one or more levels of interconnect. For example, the first interconnect structure 106 and/or the second interconnect structure 116 may comprise one or more etch-stop layers, one or more dielectric layers, one or more metal wires, one or more metal vias, one or more contacts, some other suitable interconnect features, or any combination of the foregoing.

In some embodiments, the substrate 102 may, for example, comprise silicon, some III-V material, some other semiconductor material, or the like.

In some embodiments, the plurality of semiconductor devices 104 may, for example, be or comprise metal-oxide-semiconductor field-effect transistors (MOSFETs), bipolar junction transistors (BJTs), junction field-effect transistors (JFETs), fin field-effect transistors (FinFETs), gate-all-around field-effect transistors (GAA FETs), some other suitable semiconductor device(s), or the like.

In some embodiments, the plurality of dielectric caps 112 may, for example, comprise any of silicon oxide, silicon nitride, silicon oxynitride, silicon carbide, silicon oxycarbide, silicon carbonitride, silicon oxycarbonitride, some other low-k dielectric (e.g., having a dielectric constant of less than about 3.9), some other extreme low-k dielectric (e.g., having a dielectric constant of less than about 2), or some other suitable dielectric.

In some embodiments, the first etch-stop layer 108 may, for example, comprise any of silicon oxide, silicon nitride, silicon oxynitride, silicon carbide, silicon oxycarbide, silicon carbonitride, silicon oxycarbonitride, aluminum oxide, aluminum oxynitride, or some other suitable dielectric.

In some embodiments, the plurality of metal wires 110 may, for example, comprise any of tantalum, tantalum nitride, titanium nitride, copper, cobalt, ruthenium, molybdenum, iridium, tungsten, some other conductive material, or some other suitable material.

FIG. 2 illustrates a cross-sectional view 200 of some alternative embodiments of the integrated chip of FIG. 1A in which the first dielectric cap 112 a over the first cavity 114 a has a curved lower surface.

In such embodiments, the plurality of dielectric caps 112 have curved (e.g., convex) lower surfaces that define tops of the plurality of cavities 114. For example, a bottom of the first dielectric cap 112 a is below a first point where the first dielectric cap 112 a meets the first metal wire 110 a and below a second point where the first dielectric cap 112 a meets the second metal wire 110 b.

The plurality of dielectric caps 112 may have curved lower surfaces due to a sacrificial layer (e.g., 1402 of FIG. 14 ) being recessed to form a plurality of sacrificial structures (e.g., 1502 of FIG. 15 ), where the recessing results in the plurality of sacrificial structures having curved upper surfaces (e.g., 1502 u of FIG. 15 ), and due to a dielectric layer (e.g., 1602 of FIG. 16 ) being subsequently deposited over the plurality of sacrificial structures.

Further, in some embodiments, the first interconnect structure 106 may, for example, comprise a lower etch-stop layer 106 e, a lower dielectric layer 106 d, and one or more contacts 106 c. In some embodiments, other interconnect levels and/or features may also be included.

Furthermore, in some embodiments, the second interconnect structure 116 may, for example, comprise one or more upper etch-stop layers 116 e, one or more upper dielectric layers 116 d, one or more upper vias 116 v, one or more upper metal wires 116 w, one or more upper cavities 116 c, or some other suitable features (e.g., bond pads, solder bumps, etc.). For example, in such embodiments, the one or more upper vias 116 v may be separated by the upper cavities 116 c. Further, the one or more upper metal wires 116 w may be over the one or more upper vias 116 v and also may be separated by the upper cavities 116 c. In some embodiments, other interconnect levels and/or features may also be included.

In some embodiments, any of the lower dielectric layer 106 d and the one or more upper dielectric layers 116 d may, for example, comprise any of silicon oxide, silicon nitride, silicon oxynitride, silicon carbide, silicon oxycarbide, silicon carbonitride, silicon oxycarbonitride, some other low-k dielectric (e.g., having a dielectric constant of less than about 3.9), some other extreme low-k dielectric (e.g., having a dielectric constant of less than about 2), or some other suitable dielectric.

In some embodiments, any of the lower etch-stop layer 106 e and the one or more upper etch-stop layers 116 e may, for example, comprise any of silicon oxide, silicon nitride, silicon oxynitride, silicon carbide, silicon oxycarbide, silicon carbonitride, silicon oxycarbonitride, aluminum oxide, aluminum oxynitride, or some other suitable dielectric.

In some embodiments, the one or more contacts 106 c may, for example, comprise tungsten, copper, aluminum, titanium, tantalum, or some other suitable material.

In some embodiments, any of the one or more upper vias 116 v and the one or more upper metal wires 116 w may, for example, comprise any of tantalum, tantalum nitride, titanium nitride, copper, cobalt, ruthenium, molybdenum, iridium, tungsten, some other conductive material, or some other suitable material.

In some embodiments, the one or more upper cavities 116 c may, for example, comprise air, nitrogen, oxygen, carbon dioxide, some other suitable gas having a low dielectric constant, or any combination of the foregoing.

FIG. 3 illustrates a cross-sectional view 300 of some alternative embodiments of the integrated chip of FIG. 1A in which the first cavity 114 a is defined by one or more surfaces of a first residual sacrificial structure 302 a.

In such embodiments, the plurality of cavities 114 are defined by one or more surfaces of a plurality of residual sacrificial structures 302. For example, the first residual sacrificial structure 302 a of the plurality of residual sacrificial structures 302 defines, at least in part, the first cavity 114 a of the plurality of cavities 114. The first residual sacrificial structure 302 a may, for example, be disposed on any of an upper surface of the first etch-stop layer 108, a sidewall of the first metal wire 110 a, a sidewall of the second metal wire 110 b, and a lower surface of the first dielectric cap 112 a.

In some embodiments (not shown), the first residual sacrificial structure 302 a is on all of the aforementioned surfaces such that the first cavity 114 a is enclosed by the first residual sacrificial structure 302 a. In some other embodiments, the first residual sacrificial structure 302 a is only on some of the aforementioned surfaces such that the first residual sacrificial structure 302 a only partially defines the first cavity 114 a. For example, the first residual sacrificial structure 302 a may be on the upper surface of the first etch-stop layer 108 and on sidewalls of the first and second metal wires 110 a, 110 b such that a bottom of the first cavity 114 a is defined by an upper surface of the first residual sacrificial structure 302 a while a top of the first cavity 114 a is defined by a lower surface of the first dielectric cap 112 a.

The first residual sacrificial structure 302 a may be on any of the upper surface of the first etch-stop layer 108, the sidewall of the first metal wire 110 a, the sidewall of the second metal wire 110 b, and the lower surface of the first dielectric cap 112 a because a first sacrificial structure (e.g., 1502 a of FIGS. 15 and 17 ) may not be entirely removed from said surfaces during a sacrificial structure removal process (see, for example, FIGS. 16 and 17 ).

In some embodiments, the plurality of residual sacrificial structures 302 may, for example, comprise some organic material (e.g., some carbon-based material) or some other suitable material.

Further, in some embodiments, the first interconnect structure 106 may, for example, comprise middle-of-line (MOL) interconnect. For example, the MOL interconnect may comprise one or more lower etch-stop layers 106 e, one or more lower dielectric layer 106 d, one or more contacts 106 c, one or more lower metal wires 106 w, one or more lower vias 106 v, or some other suitable features.

FIG. 4 illustrates a cross-sectional view 400 of some alternative embodiments of the integrated chip of FIG. 1A in which the first cavity 114 a is defined by the first dielectric cap 112 a and a residual dielectric structure 402.

In such embodiments, a first sidewall of the residual dielectric structure 402 extends along a sidewall of the second metal wire 110 b, and a second sidewall of the residual dielectric structure 402 opposite the first sidewall partially defines the first cavity 114 a. The residual dielectric structure 402 also extends along a sidewall of the first dielectric cap 112 a and extends between the first dielectric cap 112 a and the second metal wire 110 b. The residual dielectric structure 402 may comprise a same or different material than the first dielectric cap 112 a. For example, the residual dielectric structure 402 may comprise any of silicon oxide, silicon nitride, silicon oxynitride, silicon carbide, silicon oxycarbide, silicon carbonitride, silicon oxycarbonitride, some other low-k dielectric (e.g., having a dielectric constant of less than about 3.9), some other extreme low-k dielectric (e.g., having a dielectric constant of less than about 2), or some other suitable dielectric.

In some embodiments, the residual dielectric structure 402 may be on the sidewall of the second metal wire 110 b due to a misalignment or offset when depositing and pattering a capping layer (e.g., 1202 of FIG. 12 ) that acts as a hard mask (see, for example, FIG. 13 ). Thus, a portion (e.g., 1202 z of FIG. 12 ) of the capping layer may remain over a portion of a first dielectric structure (e.g., 904 a of FIG. 12 ) when patterning the first dielectric structure (e.g., 904 a of FIG. 12 ). As a result, the residual dielectric structure 402 may not be removed during the patterning (see, for example, FIGS. 12 and 13 ).

In some other embodiments, the residual dielectric structure 402 may be on the sidewall of the second metal wire 110 b due to a loss of selectivity when forming the capping layer (e.g., 1202 of FIG. 12 ) on a top of the second metal wire 110 b (see, for example, FIG. 12 ). Thus, a portion (e.g., 1202 z of FIG. 12 ) of the capping layer may be formed over a first dielectric structure (e.g., 904 a of FIG. 12 ). In turn, the residual dielectric structure 402 may not be removed when patterning the first dielectric structure (see, for example, FIGS. 12 and 13 ).

FIG. 5 illustrates a cross-sectional view 500 of some alternative embodiments of the integrated chip of FIG. 1A in which a first residual capping structure 502 a is over the first metal wire 110 a and a second residual capping structure 502 b is over the second metal wire 110 b.

In such embodiments, a plurality of residual capping structures 502 are on top surfaces of the plurality of metal wires 110. For example, the first residual capping structure 502 a is on a top surface of the first metal wire 110 a and the second residual capping structure 502 b is on a top surface of the second metal wire 110 b. Further, top surfaces of the plurality of residual capping structures 502 and top surfaces of the plurality of dielectric caps 112 may be approximately coplanar. Moreover, top surfaces of the plurality of dielectric caps 112 are above top surfaces of the plurality of metal wires 110.

In some embodiments, the plurality of residual capping structures 502 may be on top surfaces of the plurality of metal wires 110 due to a plurality of capping structures (e.g., 1204 of FIGS. 12 to 17 ) not being entirely removed from the tops of the plurality of metal wires 110 during a planarization process (see, for example, FIGS. 17 and 18 ).

In some embodiments, the plurality of residual capping structures 502 may comprise one or more dielectrics or one or more metals. For example, the plurality of residual capping structures 502 may, for example, comprise any of hafnium oxide (e.g., HfO), lithium niobium oxide (e.g., LiNbO), lithium nickel oxide (e.g., LiNiO), magnesium oxide (e.g., MgO), manganese oxide (e.g., MnO), molybdenum oxide (e.g., MoO), niobium oxide (e.g., NbO), nickel oxide (e.g., NiO), silicon oxide (e.g., SiO), silicon oxycarbide (e.g., SiOC), silicon oxycarbonitride (e.g., SiOCN), silicon oxynitride (e.g., SiON), silicon carbide (e.g., SiC), tin oxide (e.g., SnO), tin silicon oxide (e.g., SnSiO), strontium oxide (e.g., SrO), tantalum oxide (e.g., TaO), tantalum oxynitride (e.g., TaON), titanium oxide (e.g., TiO), titanium oxynitride (e.g., TiON), tungsten oxide (e.g., WO), zinc oxide (e.g., ZnO), zirconium oxide (e.g., ZrOx), some other suitable dielectric, tantalum (e.g., Ta), tantalum nitride (e.g., TaN), titanium nitride (e.g., TiN), copper (e.g., Cu), cobalt (e.g., Co), ruthenium (e.g., Ru), molybdenum (e.g., Mo), iridium (e.g., Ir), tungsten (e.g., W), or some other suitable metal.

FIG. 6A illustrates a cross-sectional view 600 of some alternative embodiments of the integrated chip of FIG. 1A in which the first dielectric cap 112 a surrounds the first cavity 114 a.

In such embodiments, the first dielectric cap 112 a is on a sidewall of the first metal wire 110 a, on a sidewall of the second metal wire 110 b, on a lower surface of the second interconnect structure 116 (e.g., on a lower surface of the upper etch-stop layer 116 e of FIG. 2 ), and on an upper surface of the first etch-stop layer 108 such that the first dielectric cap 112 a encloses the first cavity 114 a. In other words, the first dielectric cap 112 a extends in a closed path along a boundary of the first cavity 114 a to surround the first cavity 114 a. In yet other words, the first cavity 114 a exists within the first dielectric cap 112 a and is defined by one or more inner surfaces of the first dielectric cap 112 a.

The first dielectric cap 112 a may surround the first cavity 114 a due to the conformality and/or a fill capability of the deposition process used to form the first dielectric cap 112 a, and due to a pitch between the first metal wire 110 a and the second metal wire 110 b being small (e.g., less than 100 nanometers or some other suitable value).

In some embodiments, the second interconnect structure 116 may, for example, comprise one or more upper etch-stop layers 116 e, one or more upper dielectric layers 116 d, one or more upper vias 116 v, one or more upper metal wires 116 w, one or more upper cavities 116 c, or some other suitable features (e.g., bond pads, solder bumps, etc.). For example, in such embodiments, the one or more upper vias 116 v may be separated by the upper cavities 116 c. Further, the one or more upper metal wires 116 w may be over the one or more upper vias 116 v and also may be separated by the upper cavities 116 c. In some embodiments, other interconnect levels and/or features may also be included.

FIG. 6B illustrates a cross-sectional view 610 of some alternative embodiments of the integrated chip of FIG. 6A in which the first cavity 114 a has a different size and/or shape than a second cavity 114 b.

In such embodiments, the second cavity 114 b is adjacent to the first cavity 114 a and is separated from the first cavity by the second metal wire 110 b. Further, a width 114 aw of the first cavity 114 a is less than a width 114 bw of the second cavity 114 b. In addition, a height 114 ah of the first cavity 114 a is less than a height 114 bh of the second cavity 114 b.

Further, in some embodiments, a second dielectric cap 112 b surrounds the second cavity 114 b. In such embodiments, the first dielectric cap 112 a may extend in a first closed path along a first boundary of the first cavity 114 a to surround the first cavity 114 a and the second dielectric cap 112 b may extend in a second closed path, different from the first closed path, along a second boundary of the second cavity 114 b to surround the second cavity 114 b. For example, the second closed path may differ from the first closed path in length, shape, or the like.

The first cavity 114 a may have a different size and/or shape than the second cavity 114 b due to difference in pitch between the plurality of metal wires 110. Alternatively, the difference in the size and/or shape of the first and second cavities 114 a, 114 b may be a result of the deposition process which forms the first dielectric cap 112 a and the second dielectric cap 112 b (e.g., the difference may occur naturally during the deposition process).

In addition, in some embodiments, a third dielectric cap 112 c is adjacent to the first dielectric cap 112 a and is separated from the first dielectric cap 112 a by the first metal wire 110 a. Further, a third metal wire 110 c is adjacent to the first metal wire 110 a and is separated from the first metal wire 110 a by the third dielectric cap 112 c. In some embodiments, a cavity may not exist within the third dielectric cap 112 c. This may be because a pitch between the first metal wire 110 a and the third metal wire 110 c is substantially large (e.g., large enough that the material deposited between the first metal wire 110 a and the third metal wire 110 c to form the third dielectric cap 112 c fills a spacing between the first metal wire 110 a and the third metal wire 110 c completely).

FIG. 6C illustrates a cross-sectional view 620 of some alternative embodiments of the integrated chip of FIG. 6A in which a first residual capping structure 602 a is over the first metal wire 110 a and a second residual capping structure 602 b is over the second metal wire 110 b.

In such embodiments, a plurality of residual capping structures 602 are on top surfaces of the plurality of metal wires 110. For example, the first residual capping structure 602 a is on a top surface of the first metal wire 110 a and the second residual capping structure 602 b is on a top surface of the second metal wire 110 b. Further, top surfaces of the plurality of residual capping structures 602 and top surfaces of the plurality of dielectric caps 112 may be approximately coplanar. Moreover, top surfaces of the plurality of dielectric caps 112 are above top surfaces of the plurality of metal wires 110.

In some embodiments, the plurality of residual capping structures 602 may be on top surfaces of the plurality of metal wires 110 due to a plurality of capping structures (e.g., 1204 of FIGS. 12, 13, and 20 ) not being entirely removed from the tops of the plurality of metal wires 110 during a planarization process (see, for example, FIGS. 20 and 21 ).

In some embodiments, the plurality of residual capping structures 602 may comprise one or more dielectrics or one or more metals. For example, the plurality of residual capping structures 602 may, for example, comprise any of hafnium oxide (e.g., HfO), lithium niobium oxide (e.g., LiNbO), lithium nickel oxide (e.g., LiNiO), magnesium oxide (e.g., MgO), manganese oxide (e.g., MnO), molybdenum oxide (e.g., MoO), niobium oxide (e.g., NbO), nickel oxide (e.g., NiO), silicon oxide (e.g., SiO), silicon oxycarbide (e.g., SiOC), silicon oxycarbonitride (e.g., SiOCN), silicon oxynitride (e.g., SiON), silicon carbide (e.g., SiC), tin oxide (e.g., SnO), tin silicon oxide (e.g., SnSiO), strontium oxide (e.g., SrO), tantalum oxide (e.g., TaO), tantalum oxynitride (e.g., TaON), titanium oxide (e.g., TiO), titanium oxynitride (e.g., TiON), tungsten oxide (e.g., WO), zinc oxide (e.g., ZnO), zirconium oxide (e.g., ZrOx), some other suitable dielectric, tantalum (e.g., Ta), tantalum nitride (e.g., TaN), titanium nitride (e.g., TiN), copper (e.g., Cu), cobalt (e.g., Co), ruthenium (e.g., Ru), molybdenum (e.g., Mo), iridium (e.g., Ir), tungsten (e.g., W), or some other suitable metal.

FIGS. 7-22 illustrate cross-sectional views 700-2200 of some embodiments of a method for forming an integrated chip comprising a first metal wire 110 a and a second metal wire 110 b that are laterally separated by a first cavity 114 a. Although FIGS. 7-22 are described in relation to a method, it will be appreciated that the structures disclosed in FIGS. 7-22 are not limited to such a method, but instead may stand alone as structures independent of the method.

As shown in cross-sectional view 700 of FIG. 7 , a substrate 102 is provided. Further, a plurality of semiconductor devices 104 are formed along the substrate 102 and a first interconnect structure 106 is formed over the substrate 102.

The plurality of semiconductor devices 104 may, for example, be formed by any of an ion implantation process, a diffusion process, a deposition process, a photolithography process, or some other suitable process.

In some embodiments, the first interconnect structure 106 may comprise one or more lower etch-stop layers (e.g., 106 e of FIGS. 2 and/or 3 ), one or more lower dielectric layers (e.g., 106 d of FIGS. 2 and/or 3 ), one or more contacts (e.g., 106 c of FIGS. 2 and/or 3 ), one or more lower vias (e.g., 106 v of FIG. 3 ), one or more lower metal wires (e.g., 106 w of FIG. 3 ), or some other suitable features. In some embodiments, the first interconnect structure 106 may, for example, be formed by depositing the one or more lower etch-stop layers (e.g., 106 e of FIGS. 2 and/or 3 ) over the substrate 102, depositing the one or more lower dielectric layers (e.g., 106 d of FIGS. 2 and/or 3 ) over the etch-stop layer, patterning the one or more lower dielectric layers and the one or more lower etch-stop layers to form one or more openings in said layers, and forming the one or more contacts (e.g., 106 c of FIGS. 2 and/or 3 ), the one or more lower vias (e.g., 106 v of FIG. 3 ), and/or the one or more lower metal wires (e.g., 106 w of FIG. 3 ) in said openings.

As shown in cross-sectional view 800 of FIG. 8 , a first etch-stop layer 108 is formed over the first interconnect structure 106 and a first dielectric layer 802 is formed over the first etch-stop layer 108.

The first etch-stop layer 108 may, for example, be formed by depositing any of silicon carbide (e.g., SiC), silicon oxide (e.g., SiO2), silicon oxycarbide (e.g., SiOC), silicon nitride (e.g., SiN), silicon carbonitride (e.g., SiCN), silicon oxynitride (e.g., SiON), silicon oxycarbonitride (e.g., SiOCN), aluminum oxynitride (e.g., AlON), aluminum oxide (e.g., AlO), or some other suitable dielectric over the substrate 102 by any of a physical vapor deposition (PVD) process, a chemical vapor deposition (CVD) process, an atomic layer deposition (ALD) process, a spin-on process, or some other suitable process. A temperature during the deposition may, for example, be about 150 to 400 degrees Celsius or some other suitable value. A thickness of the first etch-stop layer 108 may, for example, be about 10 to 1000 angstroms or some other suitable value.

The first dielectric layer 802 may, for example, be formed by depositing any of silicon carbide, silicon oxide, silicon oxycarbide, silicon nitride, silicon carbonitride, silicon oxynitride, silicon oxycarbonitride, some other low-k dielectric (e.g., having a dielectric constant of less than about 3.9), some other extreme low-k dielectric (e.g., having a dielectric constant of less than about 2), or some other suitable dielectric over the substrate 102 by any of a PVD process, a CVD process, an ALD process, a spin on process, or some other suitable process. A temperature during the deposition may, for example, be about 50 to 400 degrees Celsius or some other suitable value. A thickness of the first dielectric layer 802 may, for example, be about 30 to 800 angstroms or some other suitable value.

As shown in cross-sectional view 900 of FIG. 9 , the first dielectric layer 802 and the first etch-stop layer 108 are patterned to define a plurality of dielectric structures 904 from the first dielectric layer 802. The patterning may, for example, comprise: 1) forming a mask 902 over the first dielectric layer 802; 2) performing an etch into the first dielectric layer 802 and the first etch-stop layer 108 with the mask in place; and 3) removing the mask 902. Other suitable patterning process(es) is/are however, amenable.

The mask 902 may, for example, comprise photoresist, silicon oxide, titanium nitride (e.g., TiN), or some other suitable material. The etch may, for example, comprise a wet etching process, a dry etching process, or some other suitable etching process.

As shown in cross-sectional view 1000 of FIG. 10 , a metal layer 1002 is deposited over the substrate 102 and between the plurality of dielectric structures 904. The metal layer 1002 may, for example, comprise any one or combination of tantalum (e.g., Ta), tantalum nitride (e.g., TaN), titanium nitride (e.g., TiN), copper (e.g., Cu), cobalt (e.g., Co), ruthenium (e.g., Ru), molybdenum (e.g., Mo), iridium (e.g., Ir), tungsten (e.g., W), or some other suitable material and may be deposited by any of a sputtering process, an electrochemical plating process, an electroless deposition process, a PVD process, a CVD process, an ALD process, or some other suitable process. A temperature during the deposition may, for example, be about 150 to 400 degrees Celsius or some other suitable value. A thickness of the metal layer 1002 may, for example, be about 10 to 1000 angstroms or some other suitable value.

As shown in cross-sectional view 1100 of FIG. 11 , a planarization process is performed on the metal layer 1002 to define a plurality of metal wires 110. For example, the planarization process defines a first metal wire 110 a and a second metal wire 110 b of the plurality of metal wires 110. The first metal wire 110 a and the second metal wire 110 b are laterally separated by a first dielectric structure 904 a of the plurality of dielectric structures 904 and by the first etch-stop layer 108.

The planarization process may also be performed on the plurality of dielectric structures 904. As a result, top surfaces of the plurality of metal wires 110 and top surfaces of the plurality of dielectric structures 904 may be approximately coplanar. The planarization process may, for example, be or comprise a chemical-mechanical planarization (CMP) or some other suitable planarization process.

Although FIGS. 8 to 11 illustrate the plurality of metal wires 110 as being formed by depositing the metal layer 1002 between the plurality of dielectric structures 904 and subsequently planarizing the metal layer 1002, it will be appreciated that in some alternative embodiments, the metal layer 1002 may be deposited over the first interconnect structure 106, the metal layer 1002 may then be patterned to define the plurality of metal wires 110, a dielectric layer may then be deposited over the metal wires 110 and between the metal wires to form the plurality of dielectric structures 904, and the planarization process may then be performed on the dielectric layer.

As shown in cross-sectional view 1200 of FIG. 12 , a capping layer 1202 is deposited on top surfaces of the plurality of metal wires 110 to form a plurality of capping structures 1204 on the top surfaces of the plurality of metal wires 110. For example, a first capping structure 1204 a is formed on a first top surface of the first metal wire 110 a and the second capping structure 1204 b is formed on a second top surface of the second metal wire 110 b. The capping layer 1202 and hence the plurality of capping structures 1204 may comprise one or more dielectrics, one or more metals, or some other suitable material.

In some embodiments, the capping layer 1202 is deposited over the plurality of metal wires 110 and over the plurality of dielectric structures 904 by any of a CVD process, a PVD process, an ALD process, a spin on process, an electrochemical plating (ECP) process, a sputtering process, or some other suitable process. Further, in such embodiments, the capping layer 1202 is subsequently patterned to remove the capping layer 1202 from top surfaces of the plurality of dielectric structures 904 and to define the plurality of capping structures 1204. In such embodiments, the patterning may, for example, comprise a photolithography/etching processor some other suitable patterning process. In some embodiments, a portion 1202 z of the capping layer 1202 may remain on the first dielectric structure 904 a due to a misalignment and/or offset when patterning the capping layer 1202.

In some other embodiments, the capping layer 1202 is selectively deposited so the capping layer 1202 deposits on the top surfaces of the plurality of metal wires 110 but not on top surfaces of the plurality of dielectric structures 904. The selective deposition may, for example, be performed by way of an area-selective ALD process or some other suitable selective deposition process. For example, the selective deposition process may comprise functionalizing top surfaces of the plurality of dielectric structures 904 (e.g., forming self-assembled monolayers (SAMs) or some other functional layer(s) on top surfaces of the plurality of dielectric structures 904) and depositing the capping layer 1202 by an ALD process. The functional layer(s) on the top surfaces of the plurality of dielectric structures 904 may block the capping layer 1202 from being deposited on the top surfaces of the plurality of dielectric structures 904.

In some embodiments, a small amount of the capping layer 1202 may be formed on the plurality of dielectric structures 904 during the ALD process. For example, the capping layer 1202 may be deposited on the plurality of dielectric structures 904 at a substantially slower rate than on the plurality of metal wires 110. In such embodiments, an atomic layer etching (ALE) process or some other suitable etching process may be performed to remove the small amount of capping layer 1202 from the plurality of dielectric structures 904. In some embodiments, the functionalization process, the deposition process, and the etching process may be repeated a number of times until the desired result is achieved. In some embodiments, a portion 1202 z of the capping layer 1202 may be formed on the first dielectric structure 904 a due to a loss of selectivity when forming the capping layer 1202.

A temperature during the deposition may, for example, be about 20 to 400 degrees Celsius (e.g., when the capping layer 1202 comprises a metal), about 150 to 400 degrees Celsius (e.g., when the capping layer 1202 comprises a dielectric), or some other suitable value. Further, the capping layer 1202 and hence the plurality of capping structures 1204 may have a thickness of about 10 to 1000 angstroms or some other suitable value.

The capping layer 1202 may, for example, comprise any of hafnium oxide (e.g., HfO), lithium niobium oxide (e.g., LiNbO), lithium nickel oxide (e.g., LiNiO), magnesium oxide (e.g., MgO), manganese oxide (e.g., MnO), molybdenum oxide (e.g., MoO), niobium oxide (e.g., NbO), nickel oxide (e.g., NiO), silicon oxide (e.g., SiO), silicon oxycarbide (e.g., SiOC), silicon oxycarbonitride (e.g., SiOCN), silicon oxynitride (e.g., SiON), silicon carbide (e.g., SiC), tin oxide (e.g., SnO), tin silicon oxide (e.g., SnSiO), strontium oxide (e.g., SrO), tantalum oxide (e.g., TaO), tantalum oxynitride (e.g., TaON), titanium oxide (e.g., TiO), titanium oxynitride (e.g., TiON), tungsten oxide (e.g., WO), zinc oxide (e.g., ZnO), zirconium oxide (e.g., ZrOx), some other suitable dielectric, tantalum (e.g., Ta), tantalum nitride (e.g., TaN), titanium nitride (e.g., TiN), copper (e.g., Cu), cobalt (e.g., Co), ruthenium (e.g., Ru), molybdenum (e.g., Mo), iridium (e.g., Ir), tungsten (e.g., W), or some other suitable metal.

As shown in cross-sectional view 1300 of FIG. 13 , the plurality of dielectric structures 904 are removed from between the plurality of metal wires 110. For example, the first dielectric structure 904 a is removed from between the first metal wire 110 a and the second metal wire 110 b.

In some embodiments, the plurality of dielectric structures 904 may be removed by a dry etching process or some other suitable process. For example, the plurality of dielectric structures 904 may be removed by an inductively coupled plasma (ICP) or capacitively coupled plasma (CCP) reactive ion etching (RIE) process that may utilize any one or combination of methane (e.g., CH4), fluoromethane (e.g., CH3F), difluoromethane (e.g., CH2F2), trifluoromethane (e.g., CHF3), octafluorocyclobutane (e.g., C4F8), hexafluoro-1,3-butadiene (e.g., C4F6), tetrafluoromethane (e.g., CF4), hydrogen (e.g., H2), hydrogen bromide (e.g., HBr), carbon monoxide (e.g., CO), carbon dioxide (e.g., CO2), oxygen (e.g., 02), boron trichloride (e.g., BCl3), chlorine (e.g., Cl2), nitrogen (e.g., N2), helium (e.g., He), neon (e.g., Ne), argon (e.g., Ar), or some other suitable gas. In some embodiments, a pressure during the etching may, for example, be about 0.2 to 120 millitorr or some other suitable value. A temperature during the etching may, for example, be about 0 to 100 degrees Celsius or some other suitable value. A power applied during the etching may be about 50 to 3000 watts or some other suitable value. A bias voltage applied during the etching may, for example, be about 0 to 1200 volts or some other suitable value.

In some embodiments, the plurality of capping structures 1204 may act as a hard mask during the etching process. Further, the etching process may be highly selective to the plurality of dielectric structures 904 relative to the plurality of capping structures 1204 (e.g., the plurality of dielectric structures 904 may be etched at a substantially faster rate than the plurality of capping structures 1204). For example, the etching process may remove the plurality of dielectric structures 904 a first rate and may remove the plurality of capping structures 1204 at a second rate that is slower than the first rate by a factor of about 10 or more, by a factor of 20 or more, or by some other factor.

Because the plurality of dielectric structures 904 have a high selectivity relative to the plurality of capping structures 1204 during the etching process, top surfaces the plurality of metal wires 110 may not be damaged during the etching process. For example, the plurality of capping structures 1204 may protect the top surfaces of the underlying plurality of metal wires 110 from the etching process.

Further, because of the anisotropic characteristics of the dry etching process used to remove the plurality of dielectric structures 904, the etching process may not etch away and/or damage sidewalls of the plurality of metal wires 110. For example, because the dry etching process used has little to no lateral component, sidewalls of the plurality of metal wires 110 may not be damaged during the etching.

As a result, in some embodiments, top surfaces and sidewalls of the plurality of metal wires 110 may be substantially planar. Additionally, or alternatively, the top surfaces and sidewalls of the plurality of metal wires 110 may be devoid of nanoscopic voids. Thus, a structural integrity of the plurality of metal wires 110 may not be reduced and a hence a reliability of the plurality of metal wires 110 may be high.

In contrast, were the plurality of dielectric structures 904 to be removed with an etch without the plurality of capping structures 1204 on the top surfaces of the plurality of metal wires 110, the top surfaces of the plurality of metal wires 110 could be damaged by the etch. Sidewalls of the plurality of metal wires 110 could also be damaged by the etch if the etch were performed without the plurality of capping structures 1204 in place.

FIGS. 14 to 19 illustrate cross-sectional views 1400-1900 of first embodiments for performing a remainder of the method. The acts at FIGS. 14 to 19 proceed from the acts at FIGS. 7-13 in the first embodiments of the method.

As shown in cross-sectional view 1400 of FIG. 14 , a sacrificial layer 1402 is deposited over the substrate 102 and between the plurality of metal wires 110. The sacrificial layer 1402 may take the place of the previously removed plurality of dielectric structures (e.g., 904 of FIG. 12 ). The sacrificial layer 1402 may, for example, comprise some organic material (e.g., some carbon-based material) or some other suitable material and may be deposited by any of a PVD process, a CVD process, an ALD process, a spin on process, or some other suitable process. A temperature during the deposition may, for example, be about 50 to 400 degrees Celsius or some other suitable value. The sacrificial layer 1402 may, for example, have a thickness of about 30 to 600 angstroms or some other suitable value.

As shown in cross-sectional view 1500 of FIG. 15 , the sacrificial layer 1402 is recessed to define a plurality of sacrificial structures 1502 between the plurality of metal wires 110. As a result, top surfaces of the plurality of sacrificial structures 1502 are below top surfaces of the plurality of metal wires 110 (e.g., below the first top surface of the first metal wire 110 a and below the second top surface of the second metal wire 110 b). For example, the recessing defines a first sacrificial structure 1502 a between the first metal wire 110 a and the second metal wire 110 b.

The recessing may, for example, comprise a dry etching process or some other suitable process. For example, recessing may comprise an ICP or CCP reactive ion etching (RIE) process that may utilize any one or combination of methane, fluoromethane, difluoromethane, trifluoromethane, octafluorocyclobutane, hexafluoro-1,3-butadiene, tetrafluoromethane, hydrogen, hydrogen bromide, carbon monoxide, carbon dioxide, oxygen, boron trichloride, chlorine, nitrogen, helium, neon, argon, or some other suitable gas. In some embodiments, a pressure during the etching may, for example, be about 0.2 to 120 millitorr or some other suitable value. A temperature during the etching may, for example, be about 0 to 100 degrees Celsius or some other suitable value. A power applied during the etching may be about 50 to 3000 watts or some other suitable value. A bias voltage applied during the etching may, for example, be about 0 to 1200 volts or some other suitable value.

In some embodiments, the recessing results in the plurality of sacrificial structures 1502 having curved (e.g., concave) upper surfaces 1502 u.

In some embodiments, the plurality of capping structures 1204 may act as a hard mask during the recessing process. Further, the recessing process may be highly selective to the sacrificial layer 1402 relative to the plurality of capping structures 1204 (e.g., the sacrificial layer 1402 may be etched at a substantially faster rate than the plurality of capping structures 1204).

Because the sacrificial layer 1402 has a high selectivity relative to the plurality of capping structures 1204 during the recessing process, top surfaces the plurality of metal wires 110 may not be damaged during the recessing process. Further, because of the anisotropic characteristics of the dry etching process used to recess the sacrificial layer 1402, the recessing process may not etch away and/or damage sidewalls of the plurality of metal wires 110.

As a result, in some embodiments, top surfaces and sidewalls of the plurality of metal wires 110 may remain substantially planar. Additionally, or alternatively, the top surfaces and sidewalls of the plurality of metal wires 110 may remain devoid of nanoscopic voids. Thus, a structural integrity of the plurality of metal wires 110 may be maintained and a hence a reliability of the plurality of metal wires 110 may be high.

As shown in cross-sectional view 1600 of FIG. 16 , a second dielectric layer 1602 is formed directly over the plurality of sacrificial structures 1502 and between the plurality of metal wires 110. The second dielectric layer 1602 may, for example, be formed by depositing any of silicon carbide, silicon oxide, silicon oxycarbide, silicon nitride, silicon carbonitride, silicon oxynitride, silicon oxycarbonitride, some other low-k dielectric (e.g., having a dielectric constant of less than about 3.9), some other extreme low-k dielectric (e.g., having a dielectric constant of less than about 2), or some other suitable dielectric over the substrate 102 by any of a PVD process, a CVD process, an ALD process, a spin on process, or some other suitable process. A temperature during the deposition may, for example, be about 50 to 400 degrees Celsius or some other suitable value. A thickness of the second dielectric layer 1602 may, for example, be about 30 to 800 angstroms or some other suitable value or some other suitable value.

As shown in cross-sectional view 1700 of FIG. 17 , the plurality of sacrificial structures 1502 are removed from directly below the second dielectric layer 1602 and from between the plurality of metal wires 110, thereby leaving a plurality of cavities 114 in place of the plurality of sacrificial structures 1502. For example, the first sacrificial structure 1502 a is removed from between the first metal wire 110 a and the second metal wire 110 b, thereby leaving a first cavity 114 a in place of the first sacrificial structure 1502 a.

The plurality of sacrificial structures 1502 are removed from directly below the second dielectric layer 1602 with the second dielectric layer 1602 in place. In some embodiments, the plurality of sacrificial structures 1502 may, for example, be removed by a thermal (e.g., baking) process which may vaporize the plurality of sacrificial structures 1502 and the vapor may escape the plurality of cavities 114 by passing through the second dielectric layer 1602. In some other embodiments, the plurality of sacrificial structures 1502 may be vaporized upon being exposed to a laser or a UV light. In some other embodiments, some other process(es) may be used to remove the plurality of sacrificial structures 1502 from directly below the second dielectric layer 1602.

In some embodiments, the plurality of sacrificial structures 1502 may not be entirely removed from directly below the second dielectric layer 1602 and from between the plurality of metal wires 110. As a result, a plurality of residual sacrificial structures (e.g., 302 of FIG. 3 ) may remain directly below the second dielectric layer 1602 and between the plurality of metal wires 110.

As shown in cross-sectional view 1800 of FIG. 18 , a planarization process is performed on the second dielectric layer 1602 to define a plurality of dielectric caps 112 and on the plurality of capping structures 1204 to remove the plurality of capping structures 1204 from over the plurality of metal wires 110. For example, the planarization process defines a first dielectric cap 112 a of the plurality of dielectric caps 112 that is between the first metal wire and the second metal wire 110 b, and that is directly over the first cavity 114 a.

The planarization process may also be performed on the plurality of metal wires 110. As a result, top surfaces of the plurality of metal wires 110 and top surfaces of the plurality of dielectric caps 112 may be approximately coplanar. For example, a top surface of the first metal wire, a top surface of the second metal wire 110 b, and a top surface of the first dielectric cap 112 a may be approximal coplanar. The planarization process may, for example, be or comprise a CMP or some other suitable planarization process.

Although FIGS. 16 to 18 illustrate the second dielectric layer 1602 being planarized after the plurality of sacrificial structures 1502 are removed, it will be appreciated that in some other embodiments, the second dielectric layer 1602 may be planarized before the plurality of sacrificial structures (e.g., 1502 of FIGS. 15 and 16) are removed.

Further, in some embodiments, the planarization process may not entirely remove the plurality of capping structures 1204 from over the plurality of metal wires 110. Thus, in such embodiments, a plurality of residual capping structures (e.g., 502 of FIG. 5 ) may remain over the plurality of metal wires 110.

As shown in cross-sectional view 1900 of FIG. 19 , a second interconnect structure 116 is formed over the plurality of metal wires 110 and the plurality of dielectric caps 112. The second interconnect structure 116 may, for example, be formed by repeating the aforementioned method to form one or more upper etch-stop layers (e.g., 116 e of FIG. 2 ), one or more upper dielectric layers (e.g., 116 d of FIG. 2 ), one or more upper vias (e.g., 116 v of FIG. 2 ), one or more upper metal wires (e.g., 116 w of FIG. 2 ), one or more upper cavities (e.g., 116 c of FIG. 2 ), or some other suitable features.

For example, in some embodiments, an upper etch-stop layer (e.g., 116 e of FIGS. 2 and/or 3 ) may be formed over the plurality of metal wires 110 and over the plurality of dielectric caps 112 by depositing any one or more of silicon carbide, silicon oxide, silicon oxycarbide, silicon nitride, silicon carbonitride, silicon oxynitride, silicon oxycarbonitride, aluminum oxynitride, aluminum oxide, or some other suitable dielectric over the substrate 102 by any of a CVD process, a PVD process, an ALD process, a spin on process, or some other suitable process. A temperature during the deposition may, for example, be about 150 to 400 degrees Celsius or some other suitable value. A thickness of the upper etch-stop layer (e.g., 116 e of FIGS. 2 and/or 3 ) may, for example, be about 10 to 1000 angstroms or some other suitable value.

FIGS. 20 to 22 illustrate cross-sectional views 2000-2200 of second embodiments for performing the remainder of the method. The acts at FIGS. 20 to 22 proceed from the acts at FIGS. 7-13 , while skipping the acts at FIGS. 14-19 , in the second embodiments of the method.

As shown in cross-sectional view 2000 of FIG. 20 , a second dielectric layer 2002 is formed directly over first etch-stop layer 108 and between the plurality of metal wires 110. The second dielectric layer 2002 may, for example, be formed by depositing any of silicon carbide, silicon oxide, silicon oxycarbide, silicon nitride, silicon carbonitride, silicon oxynitride, silicon oxycarbonitride, some other low-k dielectric (e.g., having a dielectric constant of less than about 3.9), some other extreme low-k dielectric (e.g., having a dielectric constant of less than about 2), or some other suitable dielectric over the substrate 102 by any of a PVD process, a CVD process, an ALD process, a spin on process, or some other suitable process. A temperature during the deposition may, for example, be about 50 to 400 degrees Celsius or some other suitable value. A thickness of the second dielectric layer 2002 may, for example, be about 30 to 800 angstroms or some other suitable value.

A plurality of cavities 114 exist within the second dielectric layer 2002 and between the plurality of metal wires 110 after depositing the second dielectric layer 2002. For example, a first cavity 114 a exists between the first metal wire 110 a and the second metal wire 110 b and is defined by one or more surfaces of the second dielectric layer 2002. The plurality of cavities 114 may exist because of the conformality and/or fill capabilities of the deposition of the second dielectric layer 2002. For example, a pitch of the plurality of metal wires 110 may be small and hence the second dielectric layer 2002 may not completely fill a space between the plurality of metal wires 110. As a result, the plurality of cavities 114 are formed within the second dielectric layer 2002 between the plurality of metal wires 110.

As shown in cross-sectional view 2100 of FIG. 21 , a planarization process is performed on the second dielectric layer 2002 to define a plurality of dielectric caps 112 and on the plurality of capping structures 1204 to remove the plurality of capping structures 1204 from over the plurality of metal wires 110. For example, the planarization process defines a first dielectric cap 112 a of the plurality of dielectric caps 112.

The planarization process may also be performed on the plurality of metal wires 110. As a result, top surfaces of the plurality of metal wires 110 and top surfaces of the plurality of dielectric caps 112 may be approximately coplanar. For example, a top surface of the first metal wire, a top surface of the second metal wire 110 b, and a top surface of the first dielectric cap 112 a may be approximal coplanar. The planarization process may, for example, be or comprise a CMP or some other suitable planarization process.

Further, in some embodiments, the planarization process may not entirely remove the plurality of capping structures 1204 from over the plurality of metal wires 110. Thus, in such embodiments, a plurality of residual capping structures (e.g., 602 of FIG. 6 ) may remain over the plurality of metal wires 110.

As shown in cross-sectional view 2200 of FIG. 22 , a second interconnect structure 116 is formed over the plurality of metal wires 110 and the plurality of dielectric caps 112. The second interconnect structure 116 may, for example, be formed by repeating the aforementioned method to form one or more upper etch-stop layers (e.g., 116 e of FIG. 6A), one or more upper dielectric layers (e.g., 116 d of FIG. 6A), one or more upper vias (e.g., 116 v of FIG. 6A), one or more upper metal wires (e.g., 116 w of FIG. 6A), one or more upper cavities (e.g., 116 c of FIG. 6A), or some other suitable features.

For example, in some embodiments, an upper etch-stop layer (e.g., 116 e of FIG. 6A) may be formed over the plurality of metal wires 110 and over the plurality of dielectric caps 112 by depositing any one or more of silicon carbide, silicon oxide, silicon oxycarbide, silicon nitride, silicon carbonitride, silicon oxynitride, silicon oxycarbonitride, aluminum oxynitride, aluminum oxide, or some other suitable dielectric over the substrate 102 by any of a CVD process, a PVD process, an ALD process, a spin on process, or some other suitable process. A temperature during the deposition may, for example, be about 150 to 400 degrees Celsius or some other suitable value. A thickness of the upper etch-stop layer (e.g., 116 e of FIG. 6A) may, for example, be about 10 to 1000 angstroms or some other suitable value.

FIG. 23 illustrates a flow diagram of some embodiments of a method 2300 for forming an integrated chip comprising a first metal wire and a second metal wire that are laterally separated by a first cavity. While method 2300 is illustrated and described below as a series of acts or events, it will be appreciated that the illustrated ordering of such acts or events are not to be interpreted in a limiting sense. For example, some acts may occur in different orders and/or concurrently with other acts or events apart from those illustrated and/or described herein. In addition, not all illustrated acts may be required to implement one or more aspects or embodiments of the description herein. Further, one or more of the acts depicted herein may be carried out in one or more separate acts and/or phases.

At 2302, a first metal wire and a second metal wire are formed over a substrate. The first and second metal wires are laterally separated by a first dielectric layer and by an etch-stop layer. FIGS. 9 to 11 illustrate cross-sectional views 900-1100 of some embodiments corresponding to act 2302.

At 2304, a first capping layer is formed on a first top surface of the first metal wire and on a second top surface of the second metal wire to form a first capping structure and a second capping structure respectively on the first and second top surfaces. FIG. 12 illustrates a cross-sectional view 1200 of some embodiments corresponding to act 2304.

At 2306, the first dielectric layer is removed from between the first metal wire and the second metal wire. FIG. 13 illustrates a cross-sectional view 1300 of some embodiments corresponding to act 2306.

Acts 2308 a, 2310 a, 2312 a, 2314 a, 2316 a, and 2318 a illustrate a first embodiment for performing a remainder of the method 2300.

At 2308 a, a sacrificial layer is deposited over the etch-stop layer and between the first and second of metal wires. FIG. 14 illustrates a cross-sectional view 1400 of some embodiments corresponding to act 2308 a.

At 2310 a, the sacrificial layer is recessed to define a first sacrificial structure between the first and second metal wires. FIG. 15 illustrates a cross-sectional view 1500 of some embodiments corresponding to act 2310 a.

At 2312 a, a second dielectric layer is deposited directly over the first sacrificial structure and between the first and second metal wires. FIG. 16 illustrates a cross-sectional view 1600 of some embodiments corresponding to act 2312 a.

At 2314 a, the first sacrificial structure is removed from directly below the second dielectric layer and from between the first and second metal wires, thereby leaving a first cavity in place of the first sacrificial structure. FIG. 17 illustrates a cross-sectional view 1700 of some embodiments corresponding to act 2314 a.

At 2316 a, the second dielectric layer is planarized. FIG. 18 illustrates a cross-sectional view 1800 of some embodiments corresponding to act 2316 a.

At 2318 a, an interconnect structure is formed over the second dielectric layer and over the first and second metal wires. FIG. 19 illustrates a cross-sectional view 1900 of some embodiments corresponding to act 2318 a.

Acts 2308 b, 2310 b, and 2312 b illustrate a second embodiment for performing the remainder of the method 2300.

At 2308 b, a second dielectric layer is deposited over the etch-stop layer and between the first and second metal wires such that a first cavity exists within the second dielectric layer and between the first and second metal wires after depositing the second dielectric layer. FIG. 20 illustrates a cross-sectional view 2000 of some embodiments corresponding to act 2308 b.

At 2310 b, the second dielectric layer is planarized. FIG. 21 illustrates a cross-sectional view 2100 of some embodiments corresponding to act 2310 b.

At 2312 b, an interconnect structure is formed over the second dielectric layer and over the first and second metal wires. FIG. 22 illustrates a cross-sectional view 2200 of some embodiments corresponding to act 2312 b.

Thus, the present disclosure relates to an integrated chip comprising one or more cavities for improving a performance of the integrate chip, and a method of forming the integrated chip for improving a reliability of the integrated chip.

Accordingly, in some embodiments, the present disclosure relates to an integrated chip comprising a substrate. A first conductive wire is over the substrate. A second conductive wire is over the substrate and is adjacent to the first conductive wire. A first dielectric cap is laterally between the first conductive wire and the second conductive wire. The first dielectric cap laterally separates the first conductive wire from the second conductive wire. The first dielectric cap comprises a first dielectric material. A first cavity is directly below the first dielectric cap and is laterally between the first conductive wire and the second conductive wire. The first cavity is defined by one or more surfaces of the first dielectric cap.

In other embodiments, the present disclosure relates to an integrated chip comprising a substrate. A first metal wire is over the substrate. A second metal wire is over the substrate and is laterally adjacent to the first metal wire. An etch-stop layer is over the substrate and is laterally between a first sidewall of the first metal wire and a second sidewall of the second metal wire. The etch-stop layer laterally separates the first sidewall from the second sidewall along bottoms of the first and second metal wires. A first dielectric cap is directly over the etch-stop layer and is laterally between the first sidewall of the first metal wire and the second sidewall of the second metal wire. The first dielectric cap laterally separates the first metal wire from the second metal wire along tops of the first and second metal wires. A first cavity is directly below the first dielectric cap and is directly over the etch-stop layer. The first cavity laterally separates the first sidewall of the first metal wire from the second sidewall of the second metal wire. The first cavity comprises a first gas. The first cavity is defined by one or more surfaces of the first dielectric cap. Further, the first sidewall of the first metal wire and the second sidewall of the second metal wire are devoid of nanoscopic voids.

In yet other embodiments, the present disclosure relates to a method for forming an integrated chip. The method comprises forming a first metal wire and a second metal wire over a substrate. The first metal wire and the second metal wire are laterally separated by a first dielectric structure. A capping layer is deposited on a first top surface of the first metal wire and a second top surface of the second metal wire at a faster rate than on a top surface of the first dielectric structure to form a first capping structure and a second capping structure respectively on the first and second top surfaces. A first etch is performed with the first capping structure and the second capping structure in place to remove the first dielectric structure from between the first metal wire and the second metal wire. The first etch removes the first dielectric structure at a faster rate than the first and second capping structures. A dielectric layer is formed between the first metal wire and the second metal wire. A first cavity is formed between the first and second metal wires after depositing the dielectric layer. The first cavity is defined by one or more surfaces of the dielectric layer.

The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. 

What is claimed is:
 1. An integrated chip comprising: a substrate; a first conductive wire over the substrate; a second conductive wire over the substrate and laterally spaced from the first conductive wire; and a first dielectric cap laterally between the first conductive wire and the second conductive wire, wherein the first dielectric cap laterally separates the first conductive wire from the second conductive wire, and wherein the first dielectric cap comprises a first dielectric material, wherein one or more surfaces of the first dielectric cap delimit a first cavity that is laterally between the first conductive wire and the second conductive wire.
 2. The integrated chip of claim 1, further comprising: an etch-stop layer directly below the first dielectric cap and the first cavity, wherein an upper surface of the etch-stop layer partially delimits the first cavity.
 3. The integrated chip of claim 2, wherein the first cavity is further delimited by a lower surface of the first dielectric cap, by a sidewall of the first conductive wire, and by a sidewall of the second conductive wire.
 4. The integrated chip of claim 1, wherein the first dielectric cap extends in a closed path along a boundary of the first cavity to surround the first cavity.
 5. The integrated chip of claim 1, wherein the first cavity is delimited, at least in part, by one or more surfaces of a first residual sacrificial structure, wherein the first residual sacrificial structure comprises an organic material different from the first dielectric material.
 6. The integrated chip of claim 1, wherein a first residual capping structure is on a top surface of the first conductive wire and a second residual capping structure is on a top surface of the second conductive wire, and wherein a top surface of the first dielectric cap, a top surface of the first residual capping structure, and a top surface of the second residual capping structure are approximately coplanar.
 7. The integrated chip of claim 1, further comprising: a second cavity adjacent to the first cavity and separated from the first cavity by the second conductive wire, wherein a width of the second cavity is greater than a width of the first cavity.
 8. The integrated chip of claim 1, wherein a first sidewall of the first dielectric cap extends along a sidewall of the first conductive wire, wherein a second sidewall of the first dielectric cap extends along a sidewall of the second conductive wire, wherein a lower surface of the first dielectric cap extends from the first sidewall to the second sidewall of the first dielectric cap, wherein the lower surface of the first dielectric cap is below a bottom of the first sidewall of the first dielectric cap and below a bottom of the second sidewall of the first dielectric cap, wherein the lower surface of the first dielectric cap delimits a top of the first cavity.
 9. The integrated chip of claim 1, further comprising: a first dielectric structure laterally between the first dielectric cap and the second conductive wire and extending along a sidewall of the second conductive wire and a sidewall of the first dielectric cap, wherein the first dielectric structure partially delimits the first cavity, and wherein the first dielectric structure comprises a second dielectric material different from the first dielectric material.
 10. An integrated chip comprising: a substrate; a first metal wire over the substrate; a second metal wire over the substrate and laterally spaced from the first metal wire; an etch-stop layer over the substrate and laterally between a sidewall of the first metal wire and a sidewall of the second metal wire, wherein the etch-stop layer laterally separates the sidewall of the first metal wire from the sidewall of the second metal wire along bottoms of the first and second metal wires; a first dielectric cap directly over the etch-stop layer and laterally between the sidewall of the first metal wire and the sidewall of the second metal wire, wherein the first dielectric cap laterally separates the first metal wire from the second metal wire along tops of the first and second metal wires; and a first cavity directly below the first dielectric cap and directly over the etch-stop layer, wherein the first cavity laterally separates the sidewall of the first metal wire from the sidewall of the second metal wire, wherein the first cavity comprises a first gas, and wherein the first cavity is delimited by one or more surfaces of the first dielectric cap, wherein the sidewall of the first metal wire and the sidewall of the second metal wire are devoid of nanoscopic voids.
 11. The integrated chip of claim 10, wherein the first cavity is delimited by an upper surface of the etch-stop layer, the sidewall of the first metal wire, the sidewall of the second metal wire, and a lower surface of the first dielectric cap.
 12. The integrated chip of claim 10, wherein the first dielectric cap is disposed on an upper surface of the etch-stop layer, the sidewall of the first metal wire, the sidewall of the second metal wire, and wherein the first dielectric cap encloses the first cavity.
 13. The integrated chip of claim 10, wherein a lower surface of the first dielectric cap that delimits a top of the first cavity is below a top surface of the first metal wire and below a top surface of the second metal wire, and wherein a top surface of the first dielectric cap, the top surface of the first metal wire, and the top surface of the second metal wire are approximately coplanar.
 14. The integrated chip of claim 10, wherein a width of the first cavity is approximately equal to a lateral distance between the first metal wire and the second metal wire.
 15. The integrated chip of claim 10, further comprising: a residual dielectric structure directly between the sidewall of the second metal wire and a sidewall of the first dielectric cap, and directly over an upper surface of the etch-stop layer, wherein the residual dielectric structure covers the sidewall of the second metal wire, and wherein a sidewall of the residual dielectric structure partially delimits the first cavity.
 16. An integrated chip comprising: a substrate; a first conductive wire and a second conductive wire laterally spaced over the substrate; a first etch-stop layer directly between a sidewall of the first conductive wire and a sidewall of the second conductive wire, the first etch-stop layer comprising a first dielectric; and a first dielectric cap directly over the first etch-stop layer and directly between the sidewall of the first conductive wire and the sidewall of the second conductive wire, the first dielectric cap comprising a second dielectric different than the first dielectric, wherein a bottom surface of the first dielectric cap, a top surface of the first etch-stop layer, and the sidewall of the first conductive wire partially form a first cavity that is directly between the sidewall of the first conductive wire and the sidewall of the second conductive wire.
 17. The integrated chip of claim 16, wherein the bottom surface of the first dielectric cap is below a top surface of the first conductive wire and a top surface of the second conductive wire, wherein the bottom surface of the first dielectric cap is above a bottom surface of the first conductive wire and a bottom surface of the second conductive wire, and wherein the bottom surface of the first dielectric cap extends continuously from the sidewall of the first conductive wire to the sidewall of the second conductive wire.
 18. The integrated chip of claim 16, further comprising: a first conductive via and a second conductive via over the first conductive wire and the second conductive wire, respectively; a second etch-stop layer over the first conductive wire, the second conductive wire, and the first dielectric cap and directly between a sidewall of the first conductive via and a sidewall of the second conductive via; and a second dielectric cap directly over the second etch-stop layer and directly between the sidewall of the first conductive via and the sidewall of the second conductive via, wherein a bottom surface of the second dielectric cap, a top surface of the second etch-stop layer, the sidewall of the first conductive via, and the sidewall of the second conductive via form a second cavity.
 19. The integrated chip of claim 18, further comprising: a third conductive wire over the first conductive via, wherein a bottom surface of the third conductive wire extends along a top surface of the first conductive via and a top surface of the second dielectric cap.
 20. The integrated chip of claim 16, further comprising: a dielectric layer extending along a top surface of the first conductive wire, a top surface of the second conductive wire, and a top surface of the first dielectric cap. 